SELF-employed people will have to file tax returns much earlier than usual next year because of the change in Budget Day to October 15.
The Budget will also have to contain a "safety fund", of perhaps €500m, in case tax revenues due in November fall below forecasts, Finance Minister Michael Noonan told the Irish Independent.
The move in the Budget from December to October is necessary under new eurozone surveillance rules known as the "two-pack". These were agreed under the Irish presidency but they will require special measures over the next 18 months.
November is a major month for tax revenues, because self-employed and people with income not taxed at source have to make a self-assessment and pay their estimated tax by the end of October.
The amount coming in is difficult to estimate in advance. Moving the Budget Day forward means the Department of Finance will not have the actual figures when the Budget is drafted.
"There can be an error of typically 1.5pc either way between estimates of revenue and the actual out-turn," Mr Noonan said.
"I will have to allow for that in the Budget arithmetic by setting aside something like that. If the estimates do not fall short, we can then put the money back into the system," he said.
As part of the same process, self-assessed taxpayers will have to make a return for 2014 earlier next year. The department will then have that figure in time for the 2015 Budget.
It has not yet been decided when the taxpayers will actually have to pay the amount due. That could be deferred to later in the year, but from 2015 there will be an earlier date for both filing a return and paying.
Mr Noonan also reiterated that the Government draws a firm distinction between low corporation tax and tax evasion. His remarks came as Austria continues a lonely battle with the other 26 EU countries to maintain the country's banking secrecy and avoid reporting foreigners' accounts to their tax authorities.
Dismissing suggestions that Austrian Foreign Minister Maria Fekter's position had left Austria under pressure and isolated, the woman who has vowed to "fight like a lion" to defend the country's banking rules insisted she had emerged on top in weekend talks with EU partners.
"I can even report a success," she said yesterday, because her counter-call to shed more light on opaque offshore trusts elsewhere was now part of an initiative by big EU countries to crack down on cross-border tax cheats.